Optical glass and lens

Abstract

The invention provides an optical glass comprising, by mass % on the oxide basis; 25 to 50% of B 2 O 3 ; 5 to 25% of ZnO: 13 to 25% of La 2 O 3 ; 10 to 28% of Gd 2 O 3 ; and 1.5 to 4% of Li 2 O, the optical glass having: a refractive index (n d ) of 1.65 to 1.76; an Abbe number (ν d ) of 45 to 60; and a molding temperature (T p ), as defined with the glass transition temperature (T g ) and the yield point (At) by the expression At+(At−T g )/ 2 , of 650° C. or less; the optical glass substantially containing neither an arsenic nor a lead nor a fluorine.

1 . An optical glass comprising, by mass % on the oxide basis;
 25 to 50% of B 2 O 3 ;   5 to 25% of ZnO:   13 to 25% of La 2 O 3 ;   10 to 28% of Gd 2 O 3 ; and   1.5 to 4% of Li 2 O,   the optical glass having:   a refractive index (n d ) of 1.65 to 1.76;   an Abbe number (ν d ) of 45 to 60; and   a molding temperature (T p ), as defined with the glass transition temperature (T g ) and the yield point (At) by the expression At+(At−T g )/2, of 650° C. or less;   the optical glass substantially containing neither an arsenic nor a lead nor a fluorine.   
   
   
       2 . The optical glass according to  claim 1 ,
 wherein the total content of La 2 O 3  and Gd 2 O 3  is 30 to 50% by mass % on the oxide basis.   
   
   
       3 . The optical glass according to  claim 1 ,
 wherein an average thermal expansion coefficient (a) in the range of 50 to 350° C. is 66×10 −7  K −1  to 84×10 −7  K −1 .   
   
   
       4 . The optical glass according to  claim 1 ,
 the optical glass has a specific gravity of 4.30 or less.   
   
   
       5 . The optical glass according to  claim 1 ,
 which has a liquidus temperature (T L ) of 970° C. or less.   
   
   
       6 . A lens comprising the optical glass according to  claim 1 .